Generally, there has been a well-known technology in this field that a seatbelt retractor is asked to facilitate the webbing upon the wearing of the seatbelt by an occupant or to prevent the drawing-out of the webbing in an emergency or abnormal state of a vehicle. However, what is considered as a problem in this technical field is the timely detection of the abnormal state of the vehicle. To do so, a webbing sensor for detecting the pulling-out acceleration of the webbing and a motion (inertia) sensor for detecting the abnormal state of the vehicle during driving due to any sudden and/or severe disruption in traveling speed, due to the impact of a collision for example, have been developed to supplement their disadvantages to each other. Herein, it is noted that the pulling-out acceleration detection of the webbing, including its responding time, must comply with the counteracted against the abrupt rotation during running and rollover in a slanted street and off-road conditions.
In respect of these points, a typical technology is U.S. Pat. No. 3,819,126 disclosing a seatbelt retractor that comprises a gear wheel actuated locking means and a web sensor configured to control a locking member mounted on the reel means to be pivoted between a locking position for preventing the rotation of the reel in the unwinding direction and a pair of release positions for allowing the reel to be rotated in the unwinding direction.
A clutch plate is mounted between a support and a reel ratchet to be biased by the spring so that a first stop supports the locking member in a pushing direction. A disabling member is rotatably mounted so that its resilient arm is connected to the support to be biased in a winding direction. An arm enlargement is fitted into the opening of the locking member to get the locking member to be supported in an unwinding direction. A wheel includes a resilient arm and a second stop, in which the resilient arm has a finger formed at its one end to be supported in the opening of the support to bias the wheel toward the disabling member. The other end of the wheel has a foot for engaging a shoulder carried by the wheel to position the second stop to abut the locking member in its intermediate release position, and the second stop disables the reel-locking device, when the belt is rapidly released or unwound from the retractor or the vehicle is in the abnormal state.
Therefore, in the abnormal state of the vehicle, as the reel is rotated rapidly in the unwinding direction by the pulling out on the belt, the inertia wheel rotates slightly with respect to the actuator to cam the pawls radially outwardly to mate with the teeth. The locking operation prevents the seatbelt from being released before less than ½ inch thereof. And then, as the coupling of a cam pawl of the actuator with the wheel ratchet is released by the spring of the clutch plate, the first stop permits the locking member to be returned to a normal position, and the second stop of the wheel forces the locking member to become disabled. The seatbelt retractor has advantages in that the webbing sensing speed is quick and the occupant restraint is performed during the traveling of the vehicle off-road.
However, in the seatbelt retractor the web sensor further includes the clutch plate, the disabling member and the wheel, so it results in causing the delay of the web sensing time due to the complex operation steps of parts for withdrawing and releasing the seatbelt. Further, in a web-sensing step the inertia wheel must be rotated at over a predetermined speed in order to expand the cam pawl outward enough to engage with the tooth of the wheel due to a relatively wider gap between them. Otherwise, the slip between them occurs.
Another technology that resolves this advantage and prevents the releasing of the webbing at a rapid speed per international standards is disclosed in Korean Patent No. 323845 corresponding to U.S. Pat. No. 5,507,448 assigned to this Applicant, which is entitled “Vehicular Seatbelt Retractor”. A web sensor adapted to this vehicular seatbelt retractor includes a mass member, which is inserted into a first tooth portion body of a clutch wheel, so that its wing latches faces a second sprocket of a retainer ring in a normal state. In other words, the mass member and the clutch wheel are rotated at the same time at any of unwinding and winding directions. But, upon the acceleration of the webbing, the mass member is instantly rotated in the webbing releasing direction, while the clutch wheel is also rotated under its inertia force. The latches pass over the tops of the teeth of the first tooth portion, so its ends are hung on the second sprocket of the retainer ring due to their centrifugal force. At that time, the rotational force of the shaft rotates the retainer. At the same time, the hook ring of the retainer forces the latch of the locking portion to be engaged with the first sprocket so as to stop the further rotation of the spool and prevent the releasing of the webbing. Then, as the releasing force of the webbing pulls the rotating stopped spool in a webbing direction to a frame or opening upper portion, the frictional tooth portions respectively formed on the opening portions become engaged with the flanges to assure the prevention of the further rotation of the spool.
The web sensor has speedy webbing sensing and a reduced number of its parts, which performs the immediate webbing stop in response to the sensing operation and facilitates the expansion of the latches while being put on the tooth top in order to reduce a gap between the latch end and a second sprocket.
But, the web sensor has a limitation in enhancing the sensing speed of the webbing and can't adjust the sensing speed and also the conversion into the normal state for enabling the web releasing, because the conversion is dependent upon the elastic degree. Also, these prior arts fail to take a countermeasure against an instant excessive load due to the reaction against the abrupt advancement of an occupant in an abnormal state of a vehicle, as the spool is stopped in response to the sensing of the webbing acceleration. For it, a web tension reducer similar to a skid mechanism of a safety seatbelt retractor disclosed in U.S. Pat. No. 6,237,869 is required, which is subject to controlling the load and often called “Load Limiter”.
In these respects, it is preferable if it is possible to positively take countermeasures against the abnormal or rollover state according to the acceleration that the web sensor senses in the collision a of a vehicle and on an off road. Also, it is preferable to adapt a tension reducer in order to control the excessive load applied to a web.
Accordingly, an object of the invention is to provide a vehicular seatbelt retractor for sensing the webbing acceleration of a seatbelt followed by an abnormal driving state of a vehicle such as collision or roll-over in time and controlling the web operation through at least one procedure in response to the webbing sensing.
Another object of the invention is to provide a vehicular seatbelt retractor for enabling a speed adjustment of a webbing acceleration sensing and providing the flexibility to the webbing control.
Another object of the invention is to provide a vehicular seatbelt retractor for enabling the winding and unwinding of sensing the web acceleration, immediately, responsive to the vehicle abnormal state and controlling the instant excessive load applied to a web of an occupant.